Collets are known in the art which have flexible split segments radially displaced by axial movement engaging a conically tapered periphery of the segments against a collet closing sleeve having internal matching taper. Such a construction is disclosed in prior art U.S. Pat. No. 3,802,713 which includes a lever operated collet chuck with a collet having screw-threads on the rear external surface thereof, and slots at the front to permit opening and closing about the work, a collet closing sleeve moved by a plurality of thrust balls housed in the chuck body and moved radially inwardly by a lever operated actuation sleeve, a geared ring in screw-threaded engagement with the collet, and a pinion turned by a key being employed for rotating the ring to adjust the collet axially into initial engagement with the work.